In a Long Term Evolution (LIE) system, Physical Downlink Control Channels (PDCCHs) are transmitted in each radio sub-frame and have a Time Division Multiplex (TDM) relationship with Physical Downlink Shared Channels (PDSCHs), as illustrated in FIG. 1A. The PDCCHs are transmitted in first N Orthogonal Frequency Division Multiplex (OFDM) symbols of a downlink sub-frame, where N may take the values 1, 2, 3 and 4, and N=4 is allowed to occur only in a system with a system bandwidth of 1.4 MHz.
In a Long Term Evolution-Advanced (LTE-A) system, the PDCCHs have been enhanced in order to further improve a demand for a capacity of PDCCH channels. For the enhanced PDCCHs, an existing solution is to transmit the enhanced PDCCHs in a PDSCH domain in the downlink sub-frame while reserving an original PDCCH domain. Existing transmission and reception schemes continue their use with the original PDCCH resources in the original PDCCH domain, for example, transmit diversity during transmission and blind detection of Downlink Control Information (DCI) in a public search space and a user equipment specific search space based upon a Cell-Specific Reference Signal (CRS) during reception; and the PDCCHs are transmitted in the first N OFDM symbols, where N may take the values 1, 2, 3 and 4, and N=4 is allowed to occur only in a system with a system bandwidth of 1.4 MHz, and this part of the PDCCH domain is referred to a legacy PDCCH domain. More advanced transmission and reception schemes can be used with a part of the original PDSCH resources in the enhanced PDCCH domain, for example, pre-coding during transmission and detection based upon a UE-Specific Reference Signal (UE-RS), i.e. a Demodulation Reference Symbol (DMRS), during reception; and the PDCCHs are transmitted over time-frequency resources beyond the legacy PDCCH domain, and this part of the PDCCH domain is referred to as an enhanced PDCCH (E-PDCCH) domain, as illustrated in FIG. 1B.
As currently specified, the E-PDCCHs can occupy resources consecutive in frequency domain, as illustrated in FIG. 1C; or can occupy resources inconsecutive in the frequency domain, as illustrated in FIG. 1D. However there has been no particular solution to transmission of DCI over the E-PDCCHs.
In summary there has been no particular solution to transmission of DCI over the E-PDCCHs so far.